The present invention relates to storage media and, in particular, it concerns non-volatile storage media that are accessible wirelessly.
By way of introduction, non-volatile storage devices are widely used in a wide variety of applications. Non-volatile storage devices include all read-write digital storage devices that retain their content when power is disconnected. Non-volatile storage devices include magnetic disks, writable optical disks, and non-volatile solid-state devices such as flash disks. From an application viewpoint, non-volatile storage devices can be categorized into three groups. The first group includes embedded storage devices, wherein the storage device is a permanent part of an electronic appliance such as a cellular telephone or a computer. The second group includes removable storage devices, wherein the storage device is easily inserted into and removed from an electronic appliance, such as, a memory card of a digital camera. The last group includes portable storage devices, wherein the storage device is a stand-alone device that can be selectively connected to appliances, for example a USB flash disk. In all three groups the non-volatile storage devices are sometimes disconnected from a power source. For example, a new cellular telephone is customarily supplied boxed with its battery disconnected from the cellular phone, a flash card of a digital camera is often removed from the camera, and a portable USB flash disk is energized only when connected to a USB port of an appliance. In all these examples, the non-volatile storage device maintains the data stored therein after power is disconnected therefrom, but the non-volatile storage device cannot be accessed to read therefrom or write thereto unless the non-volatile storage device is physically connected to a power source.
Contactless smart cards are an example of an exceptional case whereby a non-volatile memory can be accessed without the non-volatile memory being physically connected to a power source. Each contactless smart card includes a small antenna. When positioned in the proximity of a compatible base station, the antenna of the card receives sufficient electrical energy to operate the card's circuitry. The same antenna is also used to establish a wireless communication link between the contactless smart card and the base station. The wireless communication link enables the base station to read from, and in some models also write to, the smart card's non-volatile memory. This technology is applied in a variety of ways including credit-card-like plastics and key fobs. The main applications of contactless smart cards are high-speed identification and value transactions in mass transit and parking. Due to the very limited energy supply, on the one hand, and the requirement for high transaction speed, on the other hand, the amount of writable non-volatile memory in contactless smart cards is very small, with current typical memory values up to four kilobytes of EEPROM.
Thus, presently there are two types of non-volatile memories. The first type being memories with large capacities, typically in the range of Megabytes to Gigabytes. These memories require physical electrical connection for the memory to be accessed. The second type being contactless cards having small amounts of non-volatile memory, up to a few kilobytes.
There is therefore a need for a system and method for writing data onto a non-volatile memory having a large capacity when the non-volatile memory is not physically electrically connected to a power supply.